This invention concerns bead release devices used for detaching the tyre bead from the bead retaining flange of the wheel rim.
The known art teaches that to remove a tyre from the wheel rim the first operation to be carried out is to detach the tyre bead from the bead retaining flange of the wheel rim. Said operation is effected by devices, known as bead release tools, usually installed on tyre removal machines.
Said devices are generally positioned to the side of the machine casing, and comprise a horizontal arm, one end of which is hinged to said base on a vertical axis, its opposite end carrying a bead release tool in the form of a curved blade.
Said arm is associated with a pad mounted on said casing, against which the wheel. comprising the wheel rim and tyre, rests during the bead release operation.
Between the arm and the casing there is interposed a pneumatic cylinder-piston unit, provided to move said arm towards the machine casing in order to accomplish the bead release.
Although devices of this type satisfy their purpose, they present certain drawbacks.
Firstly, they operate on the wheel while at rest, and involve only a sector of the tyre edge at a time.
In addition, as the operator has to maintain the wheel at rest during tyre release, he finds himself relatively close to the region in which the tool operates, and is consequently subject to the risk of accidents.
A further drawback is the physical force which the operator has to apply to maintain the wheel at rest during bead release, and to rotate it to repeat the operation along different sectors of the tyre edge.
Finally, with bead release devices of known type the operator is compelled to turn the wheel over at least once through 180xc2x0 about a diametrical axis to be able to carry out the operation along both edges of the tyre, hence increasing the time required for the operation.
The object of the present invention is to overcome the drawbacks of the known art within the framework of a rational and reliable solution which enables the operator to dispense with the need to intervene actively during the operation.
The invention attains said object by virtue of a bead release device which, associated with rotary support means for the complete wheel rim of the tyre, acts on at least one side thereof while rotating, without any intervention by the operator.
According to the invention the device is associated with means for positioning the flange of the wheel rim in a fixed position relative to the tool of the bead release device, by virtue of the fact that the wheel rim support device can translate parallel to itself towards and away from the bead release device, or vice versa.
Preferably the bead release device is fixed in position, whereas the wheel rim support means move towards and away from it.
Moreover, the wheel rim support means are preferably such as to leave both flanges of the wheel rim free, so that the bead release device can act simultaneously on both.
Finally, the combination of the bead release device with said rotary support means for the wheel rim results in an assembly which can be easily provided with tools, of known type, for mounting and/or removing the tyre bead onto or from the flange of the wheel rim, so resulting in a complete tyre removal machine.
The particular characteristics of the invention are defined in the claims.